Journal activity type

Updating the issue summary - in discussion with @graber we decided that the free text activity could/should support this natively which means no additional plugin needed.

Looks good!
Still some minor things to improve though.

Addressed most of the feedback.

For the answer/grading display, I didn't want to add too much markup because both the questions and answers could also contain arbitrary markup which could also involve styling, bold etc., but put them in a fieldset + div wrappers.

Adjusted a bit and merged.

Automatically closed - issue fixed for 2 weeks with no activity.